You know their characters, but you don't know their faces. Say hello to the real actors behind some of movie history's greatest villains, monsters, and ghouls.

Xenomorph, Alien (1979)

Xenomorph, Alien (1979)

The Man: Bolaji Badejo

A 7-foot alien is scary enough without it slobbering K-Y Jelly from its pharyngeal jaws. Designed by Swiss surrealist H.R. Giger, Alien's "biomechanical" aesthetic changed preconceived notions about extraterrestrials on film. Giger and his team were even referred to as the "Monster Department" for their penchant to use real animal bones in many of their designs.

Desperate to find the perfect body type to play his one-of-a-kind monster, director Ridley Scott decided to cast unknown Nigerian student Bolaji Badejo, who was as skinny as he was tall, and managed to beat out Peter Mayhew (Star Wars' Chewbacca) for the role. Badejo studied mime to create a believable and sinister range of motion, which was no easy feat considering he wore a latex suit with pieces for the ribcage, legs, and tail‚ each attached separately with wires. And the sets were only about 6'6" tall, forcing Badejo to exercise caution whenever he had to move or turn quickly.There were two version of the banana-shaped head Badejo wore: a non-mechanical version for action scenes and an articulated one designed by Carlo Rambaldi for effects shots.

Scott would push Badejo, even though he could stand to be in costume for only 20 minutes before risking overheating. And one of the most difficult shots never made the final film—a scene that found Badejo suspended upside down from a wire 15 feet in the air. Badejo wore a harness around his stomach that suffocated him when he moved, and even proved too much for the stuntman brought in to do it, who ended up passing out.

Darth Vader, The Original Star Wars Trilogy (1977-1983)

Darth Vader, The Original Star Wars Trilogy (1977-1983)

The Man: David Prowse

You know the voice to be James Earl Jones. But the man inside the Sith Lord's imposing suit was David Prowse. Prowse, a British bodybuilder, caught George Lucas' eye when he appeared in Stanley Kubrick's A Clockwork Orange, and Lucas asked Prowse to choose between the fur-covered alien Chewbacca or the villainous Darth Vader. In Prowse's words, "people will always remember the villain."

A veteran of several Hammer horror films—he even co-starred with future Star Wars co-star Peter Cushing in 1973's Frankenstein and the Monster from Hell—Prowse was no stranger to being hidden behind a mask. Still, transforming into Darth Vader would present a unique set of challenges. The quilted leather suit weighed 40 pounds. Breathing would fog up the mask, while sweat would pour down the bottom of the mouthpiece, requiring Prowse to remove it every few minutes.

Despite playing such an iconic character, Prowse was never really given his due. He learned Jones would re-dub his lines only after filming wrapped, and found out one on the shocking twist (SPOILER ALERT! Darth Vader is Luke's father.) at the movie's premiere. Audiences don't even get to see Prowse's face when Vader is unmasked at the conclusion of Return of the Jedi—Lucas brought in Sebastian Shaw for the scene as a favor to Sir Alec Guinness. Prowse fought hard for the role of Superman but lost out to Christopher Reeve. However, he was asked to train Reeve for the film.